This figure illustrates the way in which a first estimator for the coherent line removal algorithm is chosen. The function is displayed for an ECG-signal s = s(t) containing CPR-artifacts. The optimal estimator for the CPR-frequency is taken as the frequency which maximizes this function. Here f is an arbitrary frequency and (kf), k = 2,3, ..., M, are its harmonics. The function ŝ = ŝ(f) is the Fourier transform of the ECG-signal s = s(t) and |ŝ(f)|2 is the powerspectrum. In the present example the optimal estimator f
0 for the CPR-frequency is f
0 = 1.66 Hz.